This French Onion Tart isn’t pretty (or easy to photograph!) but it sure is beautiful. It has sweet, jammy caramelized onions over a creamy bechamel sauce sitting on top of a buttery, flaky puff pastry… flavors don’t get more beautiful than this.
In this version I cheated and used store-bought puff pastry. And other than the béchamel (a simple white sauce), this is largely a hands-off, let-the-heat-do-the-work recipe. I’ve read and tried many shortcuts for caramelizing onions. I’ve learned to set these “hacks” aside and that the only true guarantee for jammy, sweet caramelized onions is to sauté them low and slow – that is, over a very low heat and for a long period (45 – 60 minutes).
Arliano Update (Aggiornamento Arliano):
The big news this week is that our downstairs rental apartment kitchen was installed. It’s got clean, simple lines and a sleek contemporary feel. Perfect for a rental. The study for the Eco-bonus (for energy efficiency projects) should be ready next week and then all the materials may be ordered (windows, external house insulation, solar panels, etc.). Although the kitchen is in, we’ll have to wait for painting and everything else until early next year while we wait for the supplies to come out of their backlogged status.
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Cheater’s French Onion Tart
• 3 large yellow onions, thinly sliced
• 2 tablespoons olive oil
• 1 cup whole milk, plus extra to brush pastry
• 2 tablespoons all purpose flour
• 3 tablespoons unsalted butter, divided
• 1 teaspoon kosher or sea (not table) salt, divided
• 1 teaspoon freshly ground black pepper
• 1/4 teaspoon freshly ground nutmeg
• 3 sprigs fresh thyme
• 1 garlic clove, finely minced
• 1 package rectangular puff pastry sheet
• 1/2 cup finely grated parmesan cheese (optional)
- Heat sauté pan over very low heat. Add olive oil, onions, sprigs of thyme and 1/2 teaspoon of salt and the black pepper. Stirring occasionally, sauté onions until they are caramelized and have no liquid remaining (this may take 45 – 60 minutes). If the onions are browning too quickly or sticking to the pan, add a few splashes of water as needed. Add the minced garlic and a tablespoon of butter in the last minute of sautéing. Once the onions are caramelized, remove the thyme sprigs, and let the onions cool to room temperature
- In a small saucepan, heat milk to a simmer (it’s ready when you see bubbles around the edge of pan). Or microwave the milk, if you prefer, for 2 minutes
- In a separate saucepan, over medium heat, melt the remaining 2 tablespoons of butter. Once fully melted, add the flour, and stir or whisk vigorously until the flour is fully incorporated into the butter. Cook for approximately 1 minute
- Add the heated milk, nutmeg and 1/2 teaspoon of salt to the saucepan with the butter and flour. Stir constantly until thickened, about 5 minutes. At this point you have created a béchamel sauce. If you are adding the optional Parmesan cheese, add it now and whisk it in. Once the sauce comes to a soft boil, boil for 1 minute and then reduce heat to very low and continue whisking until the sauce becomes thick like a paste. Remove from the heat and let it come to room temperature
- Place rack in the upper third of your oven. Preheat oven to 400F (200C)
- On a piece of parchment paper or a silpat mat, roll out the raw puff pastry to 11 X 13 inches (28 x 33 cm) in the shape of a rectangle. Trim away 1/2-inch (1 cm) from each side of the rectangle. Brush the edges of the puff pastry rectangle with water. Place the trimmed strips of puff pastry on the perimeter of the rectangle. This will create a nice, raised border when it bakes. Place the puff pastry on a baking sheet in the freezer for 20 – 30 minutes
- Remove the puff pastry from the freezer and prick the inner rectangle with a fork. Evenly spread the cooled béchamel paste inside the rectangle
- Evenly spread the cooled caramelized onions over the béchamel paste
- Brush the border of the puff pastry with milk
- Bake for 35-40 minutes until golden brown
- Let cool to warm or room temperature on a cooling rack (to avoid a soggy bottom). Cut into bite sized pieces for appetizers, or into 4-6 larger pieces to serve as lunch or brunch